Semiconductor device and a method of manufacturing the same and a mounting structure of a semiconductor device

ABSTRACT

The semiconductor device includes a tab including a chip supporting surface, and a back surface opposite to the chip supporting surface; a plurality of suspension leads supporting the tab; a plurality of leads arranged between the suspension leads; a semiconductor chip mounted on the chip supporting surface of the tab, the semiconductor chip including a main surface, a plurality of pads formed on the main surface, and a rear surface opposite to the main surface; a seal portion sealing the semiconductor chip such that a part of each of the leads is exposed from the seal portion; and a Pb-free solder formed on the part of each of the leads. A part of the rear surface of the semiconductor chip is contacted with the seal portion.

CROSS-REFERENCES

This is a continuation application of U.S. Ser. No. 14/108,507, filedDec. 17, 2013 which is a continuation of U.S. Ser. No. 13/357,076, filedJan. 24, 2012 (now U.S. Pat. No. 8,637,965), which is a continuation ofU.S. Ser. No. 12/897,221, filed Oct. 4, 2010 (now U.S. Pat. No.8,115,298), which is a continuation application of U.S. Ser. No.12/610,900, filed Nov. 2, 2009 (now U.S. Pat. No. 7,821,119), which is acontinuation application of U.S. Ser. No. 12/222,099, filed Aug. 1, 2008(now U.S. Pat. No. 7,777,312), which is a divisional application of U.S.patent application Ser. No. 10/879,010, filed Jun. 30, 2004 (now U.S.Pat. No. 7,804,159), which is a continuation application of U.S. patentapplication Ser. No. 10/227,817, filed Aug. 27, 2002 (now abandoned);which is a continuation application of U.S. patent application Ser. No.09/623,344, filed Aug. 31, 2000 (now abandoned); which is a 371 ofPCT/JP00/04340, filed Jun. 30, 2000. The entire disclosures of all ofthe above-identified applications are hereby incorporated by reference.

This application claims priority to JP 11-184739, filed Jun. 30, 1999and JP-2000-105251, filed Apr. 6, 2000.

TECHNICAL FIELD

The present invention relates generally to semiconductor fabricationtechnologies and, more particularly, to techniques adapted forminiaturization and thickness reduction plus cost down as well asreliability improvements.

BACKGROUND ART

Those techniques as will be explained in brief below have been takeninto consideration by the inventors as named herein during studying forreduction to practice of the present invention as disclosed and claimedherein.

The quest for further miniaturization or “downsizing” of modernelectronic equipment results in shrinkage of dimension and weightreduction and tends to grow rapidly in the markets of electronics andsemiconductor industries. Under such circumstances, it is becoming moreimportant in the manufacture of small size electronic equipment tofurther improve the large-scale integrated circuit (LSI) chip mountarchitectures—that is, to develop an improved LSI chip packagingtechnique with ultra-high integration densities.

In addition, as the markets of electronics grow, improvements inproductivity have been more strictly required while simultaneouslyreducing manufacturing costs.

A first prior known approach to satisfying the above technologicalrequirements is to employ a resin sealed or hermetic surface-mountsemiconductor device structure as disclosed in, for example, PublishedUnexamined Japanese Patent Application (“PUJPA”) No. 5-129473. The priorart device as taught thereby is such that as shown in FIG. 29, thisdevice employs a lead frame 35 with a pattern of electrical leads 33 anda chip support paddle or die pad 34, also known as a “tab” among thoseskilled in the art, being located on the same surface, wherein the priorart is featured in that the leads 33 are electrically connected at lowersurfaces to a semiconductor chip 36 via bonding wires 37, wherein thelower surfaces are for use as external electrodes each functioning as anelectrical connector portion with external circuitry operativelyassociated with the semiconductor device.

Unfortunately the first prior art shown in FIG. 29 is associated with aproblem which follows. As this is structurally designed so that the tab34's parts-mount surface side is exposed from the lower surface of thesemiconductor device, the tab 34 will possibly come into direct contactwith leads on the parts mount substrate when mounting the semiconductordevice on the mount substrate, which in turn makes it impossible to formany leads at corresponding portions of the mount substrate, resulting ina noticeable decrease in the degree of freedom of substrate designschemes. Another problem is that since the device is structurallyarranged so that the tab 34 is sealed only at its one surface, theresulting contact area between the tab 34 and a sealing material 38 useddecreases causing the tight contact or adhesiveness to degradeaccordingly, which would result in a decrease in reliability of thesemiconductor device.

A second prior art resin sealed semiconductor device is found in PUJPANo. 10-189830 (JP-A-10189830). This device is shown in FIG. 30, whichincludes a semiconductor element 42 as mounted on a tab 41 that in turnis supported by a hanging or “suspending” lead 40 of a lead frame 39,metal fine leads 45 for electrical interconnection between electrodes 43on the upper surface of said semiconductor element 42 and associativeinner leads 44, a sealing resin material 46 for use in sealing an outersurrounding region of the semiconductor element 42 containing metal finelead regions over the upper surface of semiconductor element 42, andexternal connect terminals 47 that are laid out in a bottom surfaceregion of said sealing resin 46 for connection with said inner leads 44,wherein said suspension lead 40 has been subjected to the so-called“up-set” processing thus having step-like differences 48, called“stepped portions,” and wherein the sealing resin 46 is also formed atpart underlying said tab 41 to a thickness corresponding to the amountof said upset processing.

The second prior art shown herein is such that since the suspension lead40 of the lead frame 39 has been subject to the up-set processing tohave the stepped portions 48, it becomes possible to permit the sealingresin 46 to be present at the part underlying the tab 41, which in turnmakes it possible to provide substantially the double-face sealedsemiconductor device structure with respect to the lead frame 39,thereby offering increased reliability when compared to said first priorart discussed above.

Another advantage of the prior art is that in view of the fact that thisis structurally designed to prevent exposure of the tab 41's parts-mountsubstrate side from the lower surface of the semiconductor device, thetab 41 will no longer come into contact with those leads on the mountsubstrate, thereby increasing the degree of freedom in parts mountdesign schemes.

Other examples of the semiconductor device with its tab subjected to theup-set processing (tab finishing treatment) are known among thoseskilled in the art, one of which is disclosed in JP-A-11-74440.

Regrettably said first prior art is faced with a problem in that adecrease in seal material-to-tab contact area can be lower the resultantadhesiveness thus reducing the reliability of the semiconductor devicebecause of the fact that this device is structured so that the tab issealed solely at its one surface in order to improve the thicknessreducibility.

Additionally, although said second prior art and the one as taught bythe above-identified Japanese document JP-A-11-74440 are drawn to thedouble-face resin-sealed semiconductor device with respect to the leadframe used therein, which offers an advantage as to an increase inreliability when compared to said first prior art, stepped portionsincluded are to be formed through the up-set processing whereby each ofthem suffers from a problem in that it is impossible to improve thethickness reducibility to the extent that is equivalent to the first artand also a “tab dislocation” problem including displacement or strain ofthe tab occurring during execution of such up-set Processing.

In short, it has been affirmed by the inventors that even the first andsecond prior art devices stated supra have met with limited success asto the capability of solving the conflicting or “trade-off”problems—i.e. the thickness reducibility and increased reliabilityrequired.

It is therefore a primary objective of the present invention to providea new and improved semiconductor device capable of achieving both thethickness reducibility and high reliability at a time and alsomethodology of manufacturing the semiconductor device along with a partsmount structure of the same.

Another object of this invention is to provide an improved semiconductordevice capable of increasing productivities while reducing productioncosts and a method of manufacturing the device as well as a parts mountstructure of same.

A further object of the invention is to provide a semiconductor devicecapable of-preventing any accidental electrical short circuiting andunwanted lead dropdown detachment otherwise occurring during partsmounting processes and a method of manufacturing the device as well as aparts mount structure of same.

These and other objects, features and advantages of the invention willbe apparent from the following more particular description of preferredembodiments of the invention, as illustrated in the accompanyingdrawings.

DISCLOSURE OF THE INVENTION

Some representative ones of the inventive teachings as disclosed andclaimed herein will be explained in brief below.

A semiconductor device comprising a tab supported by a plurality ofsuspension leads, a plurality of leads disposed to surround periphery ofsaid tab, a semiconductor chip mounted on one principal surface of saidtab and electrically connected to one principal surface of saidplurality of leads, and a sealing resin for sealing said plurality ofleads and said semiconductor chip plus said tab, wherein the remainingprincipal surface opposite to said one principal surface of saidplurality of leads is exposed from said sealing resin-and that said tabis less in thickness than said plurality of leads.

In addition, a method of manufacturing a semiconductor device comprisesthe steps of: preparing a matrix lead frame including a plurality oflead frames each having a plurality of leads and a tab less in thicknessthan said plurality of leads plus a suspension lead for support of saidtab; performing die bonding for mounting a semiconductor chip on or overthe tab of each said lead frame; performing wire bonding for connectionby wires between said semiconductor chip and the plurality of leads ofsaid lead frame; sealing with a sealing resin said lead frame and saidsemiconductor chip plus said wires to permit said plurality of leads tobe exposed on a lower surface side thereof; and cutting said matrix leadframe into a plurality of unitary lead portions at part in closeproximity to a seal region as sealed at said step of sealing with thesealing resin to thereby obtain a plurality of semiconductor devices.

Furthermore, a mounting structure of a semiconductor device inaccordance with the invention is a semiconductor device that is arrangedto include a pattern of electrical leads on a mount substrate, a tabsupported by a plurality of suspension leads, a plurality of leads aslaid out to surround the periphery of said tab, a semiconductor chipthat is mounted on or over one principal surface of said tab and iselectrically connected to one principal surface of said plurality ofleads, and a sealing resin Material for use in sealing said plurality ofleads and said semiconductor chip plus said tab, wherein the remainingprincipal surface on an opposite side to said one principal surface ofsaid plurality of leads is exposed from said sealing resin, and whereinan adhesive material is used to attain coupling with the other principalsurface of those leads of the semiconductor device with said tab formedto be less in thickness than said plurality of leads.

Moreover, a resin sealed semiconductor device comprises a tab forsupport of a semiconductor chip, a seal section as formed by resinsealing of said semiconductor chip, a plurality of tab suspension leadsincluding a supporting portion for use in supporting said tab and anexposed portion as coupled thereto and exposed to a surface on asemiconductor device mount side surface of said seal section, saidsupporting portion being formed to be thinner than said exposed portion,a plurality of leads disposed around said tab and exposed to saidsemiconductor device mount side surface of said seal section, and aconnection member for connection between a surface electrode of saidsemiconductor chip and a corresponding one of said leads, wherein saidtab suspension leads are coupled together via said tab.

In accordance with the instant invention, as the support portion of thetab at the tab suspension leads is formed to have a decreased thickness,it is possible to bury or embed the support portion in the seal sectionwith the sealing resin covering the same thereby enabling provision ofthe intended structure with the tab suspension lead's exposed portionbeing exposed only at the end(s) at a corner or corners on the backsurface of the seal section.

This in turn makes it possible to form an increased clearance betweenthe exposed portion of the tab suspension lead and its neighboring leadon the back surface of the seal section while at the same time enablingprevention of electrical shorting otherwise occurring when mounting thesemiconductor device on a parts mount substrate or board or else due tothe fact that the tab is buried within the seal section.

Further, a resin sealed semiconductor device is provided which comprisesa tab supporting a semiconductor chip and being smaller than saidsemiconductor chip, a seal section as formed by resin sealing of saidsemiconductor chip, a supporting portion for support of said tab, aplurality of leads disposed around said tab and exposed to asemiconductor device mount side surface of said seal section, and aconnection member for connection between more than one surface electrodeof said semiconductor chip and a corresponding one of said leads,wherein said tab and said semiconductor chip are in contact by adhesionwith each other at an inside location relative to said surface electrodeof said semiconductor chip.

According to the invention, it is possible to support the specified partat or near the end portion on the back surface of the semiconductordevice by a bonding stage including a heatup wire-bonding process. Thismakes it possible during wire bonding to apply suitable ultrasonic wavesand/or heat to wires being bonded, thereby enabling improvement inreliability and adhesiveness of such wire bonding.

In addition, a method of manufacturing a resin sealed semiconductordevice comprises the steps ‘of: preparing a lead frame including a tabcapable of supporting a semiconductor chip, a plurality of tabsuspension leads having a support section for use in supporting said taband an exposed portion coupled thereto with said support section beingthinner than said exposed portion, and a plurality of leads as disposedaround said tab; adherently securing said tab and said semiconductorchip together; using a connection member to connect a surface electrodeof said semiconductor chip to a corresponding one of said leads; forminga seal section by causing a sealing resin to flow onto an oppositesurface to a chip support surface of said tab while covering a thicknessreduced portion of said tab suspension lead with said sealing resin andthen by disposing said plurality of leads and said exposed portion ofsaid tab suspension lead on a semiconductor device mount side surface tothereby resin-mold said semiconductor chip; and subdividing said tabsuspension lead into portions at said exposed portion of said tabsuspension lead while separating said plurality of leads from a framebody of said lead frame.

BRIEF DESCRIPTION OF THE DRAWINGS

A diagram showing FIG. 1 shows a diagram of a perspective view of anexterior appearance of a semiconductor device in accordance with anembodiment 1 of the present invention.

A diagram showing FIG. 2 shows a diagram of a plan view (lower surfaceside) of the semiconductor device shown in FIG. 1.

FIG. 3 shows a plan view of a unitary lead section of the embodiment 1of the invention.

FIG. 4 shows a cross-sectional view of the unit lead section shown inFIG. 3 as taken along cutaway line A-A.

FIG. 5 shows a sectional view of the unit lead section shown in FIG. 3taken along line B-B.

FIG. 6 shows a plan view of the semiconductor device shown in FIG. 1 aspartly broken to make visible its internal configuration forillustration purposes only.

FIG. 7 shows a sectional view of the semiconductor device shown in FIG.6 taken along line C-C.

FIG. 8 shows a sectional view of the semiconductor device shown in FIG.6 taken along line D-D.

FIG. 9 shows a sectional view of the semiconductor device 1 shown inFIG. 6 taken along line E-E.

A flow diagram showing FIGS. 10A-10E show a diagram of in cross-sectiona method of manufacturing the semiconductor device in accordance withthe embodiment 1 of the invention.

FIG. 11 shows a plan view of a matrix lead frame for use duringmanufacture of the semiconductor device in accordance with theembodiment 1 of the invention.

FIG. 12 shows an enlarged plan view of main part (upper surface side) ofa unitary lead frame of the matrix lead frame shown in FIG. 11.

FIG. 13 shows an enlarged plan view of main part (lower surface side) ofthe unitary lead frame of the matrix lead frame shown in FIG. 11.

FIG. 14 shows a sectional view of the unit lead frame shown in FIG. 12taken along line F-F.

FIG. 15 shows a sectional view of the unit lead frame shown in FIG. 12taken along line G-G.

FIG. 16 shows a conceptual diagram showing a method of depositing anadhesive onto a tab at a die-bonding process step of the semiconductordevice in accordance with the embodiment 1 of the invention.

FIG. 17 shows a conceptual diagram showing a method of mounting asemiconductor chip on the tab at the die-bonding step of thesemiconductor device in accordance with the embodiment 1 of theinvention.

FIG. 18 shows a conceptual diagram showing a wire-bonding method of thesemiconductor device in accordance with the embodiment 1 of theinvention.

FIG. 19 shows a conceptual diagram showing a state in which a metalframe structure such as a metal tool and a matrix lead frame have beenaligned in position with each other at a resin sealing process step ofthe semiconductor device in accordance with the embodiment 1 of theinvention.

FIG. 20 shows a conceptual diagram showing a state in which the metaltool is clamped at the resin sealing step of the semiconductor device inaccordance with the embodiment 1 of the invention.

FIG. 21 shows a conceptual diagram showing a state in which the metaltool is disassembled at the resin sealing step of the semiconductordevice in accordance with the embodiment 1 of the invention.

FIG. 22 shows a perspective view of an exterior appearance showing astate in which the semiconductor device in accordance with theembodiment 1 of the invention has been mounted to a parts mountsubstrate.

FIG. 23 shows a sectional view of the device structure of FIG. 22 takenalong line H-H.

FIG. 24 shows a plan view of a unitary lead section of an embodiment 2of the invention.

FIG. 25 shows a sectional view of the unit lead section shown in FIG. 24take along line I-I.

FIG. 26 shows a sectional view of the unit lead section shown in FIG. 24take along line J-J.

FIG. 27 shows a partial see-through diagram of a semiconductor device inaccordance with the embodiment 2 of the invention.

FIG. 28 shows a sectional view of the semiconductor device shown in FIG.27 as taken along line K-K.

FIG. 29 shows a sectional view of the first prior art semiconductordevice that has been already discussed in the introductory part of thedescription.

FIG. 30 shows a sectional view of the second prior art semiconductordevice as also stated previously in the introductory part of thedescription.

FIG. 31 shows a plan view of an exemplary semiconductor device inaccordance with an embodiment 3 of the invention as partly broken at itssealing section to render visible its internal configuration forillustration purposes only.

FIG. 32 shows a sectional view of the semiconductor device shown in FIG.31 as taken along line L-L.

FIG. 33 shows a process flow diagram showing an example of the procedurefor assembly of the semiconductor device shown in FIG. 31.

FIGS. 34A-34E are sectional flow diagrams showing an exemplary structureper main process step in the assembly of the semiconductor device shownin FIG. 31.

FIG. 35 shows a perspective view of an exterior appearance showing anexample of the structure of a semiconductor device in accordance with anembodiment 4 of the invention.

FIG. 36 shows a bottom view of the structure of the semiconductor deviceshown in FIG. 35.

FIG. 37 shows a sectional view of the semiconductor device shown in FIG.35 taken along line M-M.

FIG. 38 shows a sectional view of the semiconductor device shown in FIG.35 taken along line N-N.

FIG. 39 shows a partial sectional view of one exemplary state at awire-bonding process step during the assembly of the semiconductordevice shown in FIG. 35.

FIG. 40 shows a partial plan view of one example of the resultantstructure when completion of molding in a semiconductor device inaccordance with an embodiment 5 of the invention, which structure ispartly broken to visualize its internal configuration for illustrationpurposes only.

FIG. 41 shows a sectional view of the semiconductor device shown in FIG.40 taken along line P-P.

FIG. 42 shows a partial plan view of an exemplary lead frame structurefor use during assembly of the semiconductor device shown in FIG. 40.

FIG. 43 shows an enlarged partial sectional view of a structure of part“T” of FIG. 41.

FIG. 44 shows an enlarged partial sectional view for showing anexemplary lead cut method at the part T of FIG. 41.

FIGS. 45A-45E are diagrams each showing a lead structure of part “Q” ofFIG. 40, wherein FIG. 45A is a bottom view, FIG. 45B is a plan view,FIG. 45C is a groove sectional view, FIG. 45D is a sectional of FIG. 45Btaken along line U-U, and FIG. 45E is a sectional view of FIG. 45B alongline V-V.

FIG. 46 shows a plan view of a modified example of the lead structure ofthe part Q of FIG. 40.

FIG. 47 shows an enlarged partial plan view of a structure of part “R”of FIG. 40.

FIGS. 48A and 48B are diagrams showing a structure of part “S”-of FIG.40, wherein FIG. 48A is an enlarged partial plan view whereas FIG. 48Bis a sectional view of FIG. 48A along line X-X.

FIGS. 49A and 49B are diagrams showing a structure of part “W” of FIG.48A, wherein FIG. 49A is an enlarged partial plan view and FIG. 49B is agroove sectional view of FIG. 49A.

FIGS. 50A-50C are diagrams showing an example of the structure of asemiconductor device in accordance with an embodiment 8 of theinvention, wherein FIG. 50A is a plan view, FIG. 50B is a side view, andFIG. 50C is a bottom view.

FIG. 51 shows an enlarged partial bottom view of a structure of part “Y”of FIG. 50C.

FIG. 52 shows a partial plan view of an exemplary structure of asemiconductor device in accordance with an embodiment 9 of the inventionas obtained at the termination of molding, the structure having aninternal configuration depicted herein as seen through a seal sectionthereof.

FIG. 53 shows a sectional view of the semiconductor device shown in FIG.52 as taken along line Z-Z.

FIG. 54 shows an enlarged partial sectional view of a structure of thedevice at part “AB” of FIG. 53.

FIG. 55 shows an enlarged partial sectional view diagram showing oneexample of a method of cutting leads at the part “AB” of FIG. 53.

FIGS. 56A-56D are partial sectional diagrams showing an etching methodthat is one example of a lead frame machining method used for assemblyof the semiconductor device in accordance with the invention.

FIGS. 57A-57D are partial sectional diagrams showing an etching methodas one example of a lead frame machining method used for assembly of thesemiconductor device in accordance with the invention.

FIGS. 58A-58D are partial sectional diagrams showing an etching methodas one example of a lead frame machining method used for assembly of thesemiconductor device in accordance with the invention.

FIGS. 59A-59C are partial sectional diagrams showing a pressing methodas one example of a lead frame machining method used for assembly of thesemiconductor device in accordance with the invention.

FIGS. 60A-60C are partial sectional diagrams showing a pressing methodas one example of a lead frame machining method used for assembly of thesemiconductor device in accordance with the invention.

FIGS. 61A-61C are partial sectional diagrams showing a press method asone example of a lead frame machining method used for assembly of thesemiconductor device in accordance with the invention.

FIG. 62 shows a partial plan view of an exemplary structure of asemiconductor device in accordance with a variant of the invention asobtained at the termination of molding, the structure having an internalconfiguration depicted herein as seen through a seal section thereof.

FIG. 63 shows a sectional view of the semiconductor device shown in FIG.62 taken along line CC-CC.

FIG. 64 shows a partial plan view of an exemplary structure of asemiconductor device in accordance with another variant of the inventionas obtained at the termination of molding, the structure having aninternal configuration depicted herein as seen through a seal sectionthereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a detailed description of several embodiment of the invention setforth below, any explanation as to the same or like components will notbe repeated in principle, except as otherwise believed necessary.

Also note that although in the description of embodiments below anexplanation will be given with subdivision into a plurality of sectionsor preferred forms for reduction to practice of the invention, these arenot the ones having no relation to one another and are in certainrelation that one is a modified example or detailed one or additionalexplanation of part or the whole of another, except as otherwiseindicated specifically.

Further note that in the description of embodiments below, those numberof constituent parts or components as used therein (including piecenumbers, values, quantities, ranges, etc.) are mere examples and theinvention should not be limited only to such specific quantity and anyappropriate numbers that are greater or less than the specific numbersmay also be employable on a case-by-case basis, except as otherwiseindicated specifically and also except for certain cases where theinvention is apparently limited to specific numbers in a viewpoint ofprinciples thereof.

Some preferred embodiments of the present invention will now beexplained in detail with reference to the accompanying drawings. Notehere that in all of the attached drawings for use in explaining suchembodiments, those members with the same functionalities are designatedby the same reference characters or numerals and any repetitiveexplanation thereof will be eliminated therein.

Embodiment 1

FIG. 1 is a diagram showing a perspective view of an exterior appearanceof a semiconductor device in accordance with an embodiment 1 of thepresent invention; FIG. 2 is a diagram showing a plan view (lowersurface side) of the semiconductor device; and FIG. 3 depicts a planview of a unitary lead section (details will be described later) of theembodiment 1, wherein broken lines indicate a seal region. FIG. 4 is across-sectional view of the unit lead section of FIG. 3 as taken alongline A-A; FIG. 5 is a sectional view of the unit lead section of FIG. 3taken along line B-B; FIG. 6 is a plan view of the semiconductor deviceof FIG. 1 as partly broken to make visible its internal configurationfor illustration purposes only; FIG. 7 is a sectional view of thesemiconductor device of FIG. 6 taken along line C-C; FIG. 8 is asectional view of the semiconductor device of FIG. 6 taken along lineD-D; and, FIG. 9 is a sectional view of the semiconductor device 1 ofFIG. 6 taken along line E-E.

As shown in FIGS. 1 and 2, the semiconductor device 1 of theillustrative embodiment 1 is a semiconductor device of the areal or“surface” mount type which is structurally arranged so that electricalleads 2 for use as external connection terminals are partly exposed atouter periphery of the semiconductor device on its lower surface side.This semiconductor device 1 includes a thin plate that is made ofcopper-or iron-based materials and machined to have a desired shape. Asshown in FIGS. 3-5, this thin plate has a centrally disposed chipsupport paddle or die pad (also called “tab”) 5 that is supported byfour suspending leads (referred to as tab suspension leads hereinafter)4 which are integrally formed with the “tab” pad 5, and a plurality ofleads 2 laid out surrounding said tab 5. This thin plate will bereferred to as a unit lead section 3 hereinafter.

The lower surface side of said tab suspension leads 4 (excluding outerend portions) and tab 5 is subjected to etching treatment so that theresultant thickness is approximately half of the thickness of otherportions. This processing is generally called half-etching treatment. Inthis-way, the unit lead section 3 of the embodiment 1 has on its lowersurface side a stepped portion 6 due to such half-etching treatment. Asemiconductor chip 8 is mounted on an upper surface (one principalsurface) of the tab 5 of said unit lead section 3 as shown in FIGS. 6-8.The semiconductor chip 8 may include certain integrated circuitry suchas a microcomputer, application-specific integrated circuit (ASIC), gatearray, system large-scale integrated circuit (LSI), memory or the like,and a plurality of electrical connection pads 7 made of aluminum (Al) orother similar suitable conductive materials for use as externalconnection terminals of the integrated circuitry. The semiconductor chip8 is rigidly bonded by adhesive 9 such as nonconductive paste ornonconductive films with the integrated circuitry facing upwardly.

Respective pads 7 of this semiconductor chip 8 are electricallyconnected to one principal surface of said leads 2 via conductive wires10 made of gold (Au) or Al or else. Said semiconductor chip 8, wires 10,tab 5, tab suspension leads 4 and leads 2 (upper surface portions andside surface portions) are sealed by a sealing resin material 11including but not limited to epoxy resin or silicon resin for thepurposes of improvement in protectiveness and humidity resistivity. Notehowever that the lower surface portions (the other principal surface) ofthe leads 2 for use as external terminals are exposed on the lower sidesurface side of the semiconductor device.

Those portions sealed by the sealing resin 11 will be referred tohereafter as sealed portions 12. As seen from FIG. 9, a respective oneof said leads 2 is specifically fabricated so that its upper surface isgreater in area than the exposed lower surface in order to preventunwanted dropdown detachment from the sealed portion 12 thereof.

In addition, in order to improve the humidity resistivity and alsoincrease the parts mount abilities when mounting the semiconductordevice 1 on its associative mount substrate, the leads 2 as exposed fromthe semiconductor device are subject to external packaging processingincluding but not limited to soldering metallization using Pb—Sn-basedsoldering processes.

A thin-film fabricated through external packaging processes will bereferred to as metallized or metal-plated portion 13 hereafter. Saidexternal packaging may also be done by metal-plating techniques using Pbfree solder materials such as Sn—Ag or Sn—Zn-based ones. Designing saidmetal-plated portion to have a thickness of about 10 micrometers (μm)makes it possible for the semiconductor device 1 to retain a stand-offfrom the lower surface of the sealed portion 12, which corresponds tothe thickness of the metal-plated portion 13. The plated portion 13 isnot depicted in FIGS. 2 and 4 for purposes of convenience inillustration only.

In this way, the semiconductor device 1 of this embodiment is such thatunlike the prior art with its stepped portion 6 formed by foldingmachining (up-set processing), the stepped portion 6 is formed byhalf-etching techniques thereby permitting the sealing resin 11 to existat such locations; thus, it becomes possible to seal the tab 5 and tabsuspension leads 4 with the sealing resin 11 while at the same timerealizing the intended thickness-reduced structure, which in turn makesit possible to avoid the problem as to the degradation of reliabilityotherwise occurring due to a decrease in close contact or adhesivenessas resulted from a decrease in contact area between the sealing resin 11and the tab 5.

Another advantage of the embodiment is that letting the lower surfacesof the leads 2 be exposed from the lower surface of the sealing section12 of the semiconductor device 1 for use as external connectionterminals makes it possible to prevent deformation of leads duringcarriage and/or mounting processes to thereby improve the reliability.In addition, as the leads 2 are projected by little degree from the sidesurfaces of the seal section 12, it is possible to achieveminiaturization or “shrinkage” of planar size of the semiconductordevice 1. Additionally, as said leads 2 are arranged so that the uppersurface sealed is greater in area than the lower surface exposed,sufficiently enhanced adhesiveness is obtainable to thereby enableretainment of increased reliability, irrespective of the fact that theeffective bonding surface with respect to the seal resin 11 consistsessentially of the upper and lower surfaces.

One example of a method of manufacturing the above-noted semiconductordevice 1 in accordance with the embodiment 1 of the invention will nextbe explained with reference to a flow diagram of FIG. 10 along withFIGS. 11 to 21 below.

FIG. 11 is a diagram showing a plan view of a matrix lead frame for usein the manufacture of the semiconductor device in accordance with saidembodiment 1; FIG. 12 shows an enlarged plan view (upper surface side)of a unit Lead frame (details will be explained later) of the matrixlead frame of FIG. 11; FIG. 13 is an enlarged plan view (lower surfaceside) of the unit lead frame of the matrix lead frame of FIG. 11; FIG.14 is a cross-sectional view of the structure of FIG. 12 as taken alongline F-F; and, FIG. 15 is a sectional view of the structure of FIG. 12taken along line G-G.

The matrix lead frame 14 shown herein is formed through patterning of acopper- or iron-based metal plate by etching techniques. As shown inFIG. 11, the matrix lead frame 14 is arranged so that a specified numberof regions (referred to hereafter as unit lead frame 15) eachcorresponding to the surface area of a single semiconductor device 1 areformed thereon—here, ten separate equally spaced regions consisting oftwo rows extending in a direction along long sides and five columnsalong short sides, by way of example.

Additionally formed at the peripheral edges of each unit lead frame 15is slits (referred to hereafter as stress relax slits 16) used forrelaxation of stress forces as will possibly be applied to the matrixlead frame 14 during manufacturing processes, with guide pins 17 for useas supporting and position alignment pins during manufacturing beingformed along the long sides of the matrix lead frame 14.

As shown in FIGS. 12-13, a tab 5 is centrally disposed over the unitlead frame 15 while being supported by its associated four tabsuspension leads 4, wherein a plurality of leads 2 are provided at thoselocations in close proximity to the tab 5 in such a manner as tosurround the tab 5, these leads being supported by the frame. The lowersurface side of said tab suspension leads 4 (excluding outer endportions) and tab 5 is subjected to half-etching treatment so that theresultant thickness is about half of the thickness of other portions ofthe unit lead frame 15.

In this way the unit lead frame 15 of the embodiment 1 has a steppedportion 6 on its lower surface side as shown in FIGS. 14-15. Thisstepped portion 6 is not the one that is formed at a separate processstep (referred to as after- or post-treatment hereafter) aftercompletion of patterning using either punching or etching methods as inthe prior art, but the one that permits simultaneous execution of bothpatterning and half-etching at a time; thus, it is possible to reducecosts for mass production of the matrix lead frame 14. Additionally thematrix lead frame 14 of the embodiment 1 does no longer requirefold/bend machining processes applied to the matrix lead frame aftercompletion of patterning as in the prior art, which in turn makes itpossible to prevent occurrence of problems such as tabdisplacement/strain defects due to such bend/fold machining.

An explanation will next be given of a method of fabricating the matrixlead frame 14 shown in FIGS. 11-15 below.

FIG. 16 is a conceptual diagram showing a method of depositing adhesiveonto a tab; FIG. 17 is a conceptual diagram showing a method of mountinga semiconductor chip on the tab; FIG. 18 is a conceptual diagram showinga wire-bonding method; FIG. 19 is a conceptual diagram showing the statein which a metal frame structure such as metal tool and a matrix leadframe have been position-aligned at a resin sealing process step; FIG.20 is a conceptual diagram showing the state in which the metal tool isclamped at the resin sealing step; and, FIG. 21 is a conceptual diagramshowing the state in which the metal tool is disassembled at the resinsealing step.

Firstly, as shown in FIG. 10A, make use of an adhesive 9 such asconductive paste or nonconductive paste or nonconductive film or else tobond a semiconductor chip 8 to each tab 5 of the matrix lead frame 14.First, as shown in FIG. 16, deposit the adhesive 9 on each tab 5 by useof a syringe 18; thereafter, as shown in FIG. 17, use a collet 19 tomount the semiconductor chip 8 on each tab 5 with the adhesive 9deposited thereon. This process step will be referred to as die bondingstep hereinafter.

Next, as shown in FIG. 10B, let respective pads 7 of the semiconductorchip 8 be electrically connected to corresponding leads 2 by conductivewires 10 made of Au or the like. This process begins with a step ofrigidly attaching the matrix lead frame 14 with the semiconductor chip 8mounted thereon to a bonding stage 20 as heated up to high temperaturesas shown in FIG. 18. Then, while retaining the rigid fixed state,electrically connect respective pads 7 of the semiconductor chip 8 bywires 10 made of Au or else to respective leads 2 of a correspondingunit lead frame 15 by using a capillary 21. This process will bereferred to hereafter as wire bonding step.

Next, as shown in FIG. 10C, use a transfer molding method to seal uppersurfaces and sidewall regions of the semiconductor chip 8 and wires 10plus tab 5 along with tab suspension leads 4 (not shown) and leads 2with a sealing resin material 11 including but not limited to epoxyresin or silicon resin. This process begins with a step of mounting thematrix lead frame 14 with the wire bonding applied thereto at aspecified position of a lower metal mold tool 22 of transfer moldingapparatus, thereby tightly clamping its upper metal tool 23 and lowermetal tool 22 together. The both metal tools thus clamped have an innerspace (referred to as cavity 24 hereafter) that is defined at a levelcorresponding to the mating surface thereof, which space permits thesemiconductor chip 8 and wires 10 plus tab 5 along with tab suspensionleads 4 (not shown) and leads 2 (upper. surface and side surfaceportions) to be sealed with the sealing resin 11.

Next, as shown in FIG. 20, while letting the metal tools be tightlyclamped together, fill the sealing resin 11 into each said cavity 24through a runner 25 and gate 26 which define a resin flow path. The sealresin 11 filled attempts to flow around the half-etched tab 5 and thestepped portion 6 of the lower surface of the tab suspension leads 4(not shown) thereby air-tightly sealing the semiconductor chip 8, wires10, tab 5, tab suspension leads 4 (not shown), and leads 2 (uppersurface portions and side surface portions). At this time the lowersurface of said leads 2 and the lower surface of the seal section 12 areon substantially the same plane while allowing the lower surface ofleads 2 to be exposed from the lower surface of seal section 12.

Note here that it will be desirable that outer end portions of saidleads 2 be projected outwardly from side surfaces of the sealing section12 in order to facilitate cutting at cutting process steps. Thereafter,as shown in FIG. 21, the metal tool structure is disassembled. Thisprocess will be referred to hereafter as resin sealing step.Additionally, although the above-noted resin sealing step isillustratively designed to employ transfer molding methods, sheetmolding methodology may alternatively be used for performing resinsealing while letting a thermal resistive sheet be uniformly spreadcovering the surfaces of the upper metal tool 23 and lower metal tool 22and retaining such state. In this case the leads 2 are projected fromthe seal section 12 by a degree corresponding to an amount of sinkageinto said sheet.

Next, as shown in FIG. 10D, execute external packaging of those leads 2as exposed from the seal section 12 for the purposes of improvement inhumidity resistivity and also improvement of mountability when mountinga semiconductor device onto a parts mount substrate. Preferably saidexternal packaging is done by solder metallization techniques usingPb—Sn-based solder materials; however, other similar techniques mayalternatively be employable, including but not limited to metallizingmethods using Pb-free solders such as Sn—Ag-based, Sn—Zn-based ones.Designing said metal-plated portion 13 to have a thickness of about 10permits the semiconductor device 1 to attain stand-off corresponding indimension to the thickness of the metallized portion 13. Hereinafter,this process will be collectively called an external packaging processstep.

Next, as shown in FIG. 10E, use a cutting metal mold structure (notshown) to cut the matrix lead frame 14 at specified positions lyingslightly outside of each sealing section 12 thereby subdividing it intoa plurality of unit lead sections 3 (those portions of the unit leadframe 15 with frames removed away therefrom) so that the semiconductordevice 1 shown in FIG. 1 is thus obtained. This process will becollectively referred to as cutting step hereinafter.

Semiconductor devices 1 thus manufactured in the way stated supra arethen subjected to a product screening delivery inspection/test procedurefor separation of good products from defective ones, the former will beplaced in condition for shipment. As apparent from the foregoing, themanufacturing method discussed above is free from a need to apply anyfold/bending machining processes to external terminals of semiconductordevices under manufacture; thus, it is possible to make easier processmanagement required therefor to thereby increase productivities. Anotheradvantage is that in regard to almost all process steps, currentlyestablished semiconductor manufacturing apparatus or equipment may beemployable without requiring any substantive modifications, which inturn makes it possible to greatly reduce or avoid risks as to new plantinvestment.

It should be noted that although in the manufacturing method statedabove the external packaging is carried out by solder metallizationtechniques, the invention should not exclusively be limited thereto andmay alternatively be modifiable in such a manner that a matrix leadframe 14 may be prepared which is such that external packaging treatmentsuch as Pd metallization or the like has been applied in advance tothose lead regions as exposed from semiconductor devices. In this casethe external packaging process is no longer required during themanufacture of the semiconductor device 1 whereby the requisite numberof process steps may be reduced thus increasing productivitiesaccordingly.

It should also be noted that although the cutting process noted above isdone by use of the cutting metal mold structure, this may alternativelybe modified so that in a way similar to the process of dicingsemiconductor chips out of a wafer, a dicing blade is used to cut intorespective unit lead sections 3 after having applied a dicing tape ontothe lower surface of the matrix lead frame 14. In this case, it becomespossible to attain the intended cutting at specified locations at ornear the seal section 12 because of the absence of any structurallimitations when compared to the case of cutting by using a cuttingmetal mold tool, thereby narrowing a gap distance between adjacent onesof the unit lead frames 15, which in turn makes it possible to improvethe utilization efficiency of the matrix lead frame 14. In addition,since in this case the leads 2 are not projected from side surfaces ofthe seal section 12, it is possible for the resultant semiconductordevice to decrease or “shrink” in planar dimensions in comparison withthe case of cutting by using the cutting metal mold tool.

Additionally, although in the above noted manufacturing method thematrix lead frame 14 is prepared which has its stepped portion 6 asformed by half-etching techniques, the invention should not be limitedonly to this approach and may alternatively be modified so that a matrixlead frame 14 is prepared with its stepped portion 6 being formedthrough coiling patterning techniques.

FIG. 22 is a diagram showing a perspective view of an exteriorappearance showing the state that the semiconductor device in accordancewith the embodiment 1 has been mounted to a parts mount substrate, andFIG. 23 is a sectional view of the device structure of FIG. 22 takenalong line H-H. To mount this semiconductor device 1 onto the partsmount substrate 27, a method is employable which includes the steps ofcoating or “painting” a chosen bonding material such as cream solders orthe like on leads 28 of the mount substrate 27 which correspond to thoseleads 2 on the lower surface of a sealing section 12 of thesemiconductor device 1, temporarily attaching the semiconductor device 1to the leads 28 of mount substrate 27 with the bonding material 29coated thereon, and thereafter performing reflow processes in a heatingfurnace (not shown).

As shown in FIG. 23, the semiconductor device 1 of the embodiment 1 isas thin as 1 mm, or more or less, in height when mounted whilesimultaneously permitting its planar dimensions to be significantlysmaller than those packages with leads projecting outwardly from lateralsides of a seal section, which packages typically include quad flatpackage (QFP) structures, thus enabling achievement of high-densitymountabilities. It is also possible to prevent occurrence of anyunwanted electrical shorting between the tab and leads on a parts-mountsubstrate because of the fact that each tab is not exposed from thelower surface of its associated semiconductor device unlike the priorart.

Embodiment 2

FIG. 24 is a diagram showing a plan view of a unitary lead section of anembodiment 2 of the invention. Note that broken lines are used in FIG.24 to indicate a seal region. FIG. 25 depicts a cross-sectional view ofthe unit lead section of FIG. 24 as take along line I-1; FIG. 26 is asectional view of the unit lead section of FIG. 24 take along line J-J;FIG. 27 is a partial see-through-diagram of a semiconductor device inaccordance with the embodiment 2; and, FIG. 28 is a sectional view ofthe semiconductor device of FIG. 27 taken along line K-K.

A difference of the embodiment 2 from embodiment 1 is that whereas theembodiment 1 is the structure capable of sealing each tab 5 and tabsuspension leads 4 with the sealing resin 11 because of the presence ofthe stepped portion 6 on the lower surface side of such tab suspensionleads 4 (excluding outer end portions) and tab 5, the embodiment 2 isarranged to have another stepped portion 6 at distal end portions on thetab 5 side of the leads 2 (referred to hereafter as inner end portions31) in addition to the lower surface side of the tab suspension leads 4(excluding outer end portions) and tab 5, thereby making it possible toseal the inner end portions 31 of leads 2 in addition to such tab 5 andtab suspension leads 4. The remaining parts of the embodiment 2 aresubstantially the same as those of the embodiment 1; thus, onlydifferent points will be explained below, and an explanation as to suchsimilar points will be eliminated herein.

As shown in FIGS. 24 to 26, a unit lead section 3 of the embodiment 2has a centrally located tab 5 that is supported by four tab suspensionleads 4, wherein a plurality of leads 2 are provided to surround saidtab 5. Said tab suspension leads 4 (excluding external end portions) andthe tab 5 plus inner end portions 31 of the plurality of leads 2 aresubjected to half-etching treatment to have a thickness about half ofthat of the other portions.

Additionally, in order to prevent accidental contact between the leads 2and tab suspension leads 4, bevel machining is applied to respectiveleads 2 lying nearest to the tab suspension leads 4 at their corneredges 32 opposing the tab suspension leads 4. As shown in FIGS. 27-28, asemiconductor chip 8 is mounted and secured on the tab 5 by adhesive 9such as nonconductive paste or nonconductive film or else. Thissemiconductor chip 8 has respective pads 7 which are electricallyconnected to said plurality of leads 2 via conductive wires 10 made ofAu or Al or the like.

It is noted that the semiconductor chip 8, wires 10, tab 5, tabsuspension leads 4 and leads 2 (upper surface portions and side surfaceportions plus lower surfaces of inner end portions) are sealed by asealing resin material 11 including but not limited to epoxy resin orsilicon resin for the purposes of improvement in protectiveness andhumidity resistivity. Note however that the lower surfaces of outer endportions 30 of the leads 2 for use as external connection terminals areexposed on the lower surface side of the semiconductor device 1. In thisway, the semiconductor device 1 of the embodiment 2 is arranged so thatthe inner end portions 31 of the leads 2 are subjected to half-etchingtreatment to form a stepped portion 6 which is then sealed by thesealing resin 11, thereby enabling the inner end portions 31 of leads 2to have relatively free shapes.

More specifically, the lower surfaces of the leads 2 as exposed from theseal section 12 are limited in shape to those based on standards andregulations of the Electronic Industries Association of Japan (EIAJ);however, in regard to the leads 2 within the seal section 12, nospecific standards are present thus making it possible to freely designthe shape and lead pitch values thereof into optimal ones in a waypursuant to the size of semiconductor chip 8 and also the number of padsused.

The embodiment 2 offers similar advantages to those of the embodiment 1in that i) it has the stepped portion 6 as formed by half-etchingtreatment, ii) the sealing resin 11 is capable of being exist at suchlocation, iii) the lower surfaces of the leads 2 are exposed from thelower surface of the semiconductor device 1 for use as external connectterminals, and iv) the leads 2 are projected by a very little amountfrom side surfaces of the seal section 12; in addition, regarding theinner end portions 31 of the leads 2, it is possible to appropriatelydesign the shape and lead pitch values thereof into optimal ones in away pursuant to the size of semiconductor chip 8 and also the number ofpads because of the fact that the stepped portion 6 is formed byhalf-etching techniques on the lower surfaces of the inner end portionsof leads 2 and is then sealed by the seal resin 11.

Embodiment 3

FIG. 31 is a diagram showing a plan view of an exemplary semiconductordevice in accordance with an embodiment 3 of the present invention whileletting a sealing section be partly broken to make visible its internalconfiguration for illustration purposes only; FIG. 32 depicts across-sectional view of the semiconductor device shown in FIG. 31 astaken along line L-L; FIG. 33 is a process flow diagram showing anexample of the procedure for assembly of the semiconductor device shownin FIG. 31; and, FIGS. 34A-34E are sectional flow diagrams showing anexemplary structure per main process step in the assembly of thesemiconductor device shown in FIG. 31.

The semiconductor device of the embodiment 3 is generally similar to thesemiconductor device as set forth in conjunction with the embodiment 2discussed above, and is a quad flat non-leaded (QFN) package 49 of theperipheral type with a plurality of leads 2 being disposed at theperiphery of a back surface 12 a of its sealing section 12(semiconductor device mounting surface side).

Accordingly, only characteristic portions of the QFN package 49 will beexplained here, and any explanation as to the same portions as those ofthe embodiment 2 will be eliminated.

The QFN package 49 is structurally arranged to include a tab 5supporting thereon a semiconductor chip 8, a sealing member 12 with thesemiconductor chip 8 sealed by resin, tab suspension leads 4 for supportof the tab 5, a plurality of leads 2 which are disposed around the tab 5and exposed to a back surface 12 a of the sealing member 12 while havinga thickness-increased portion 2 a and thickness-reduced portion 2 bthinner than the portion 2 a for formation of a stepped portion withrespect to a thickness direction, wires 10 which are connecting membersfor electrical connection between bonding pads (electrodes) 7 of thesemiconductor chip 8 and those leads 2 corresponding thereto, and anadhesive 9 such as silver paste for use in bonding the semiconductorchip 8 and tab 5 together.

More specifically, in the QFN package 49 shown in FIGS. 31-32, thethickness-increased or “thick” portion 2 a and thickness-reduced or“thin” portion 2 b are provided at a respective one of the leads 2disposed at the periphery of the back surface 12 a of sealing member 12whereby the thick portion 2 a of such lead 2 is exposed to the peripheryof the back surface 12 a of sealing member 12 while causing the thinportion 2 b to be covered or coated with a sealing resin material 11.

In short, the leads 2 are each formed to provide the thin portion 2 bthat is less in thickness than the thick portion 2 a, wherein one ofthem—i.e. thick portion 2 b to which a wire 10 is to-be-connected—isburied in the sealing member 12 to function as an inner lead whereas theother, i.e. thick portion 2 a, has its surface exposed to the backsurface 12 a of such sealing member 12, which is for use as ato-be-connected portion 2 c functioning as an outer lead.

Additionally in the QFN package 49, the tab 5 is supported by the tabsuspension leads 4, and, as shown in FIG. 37 regarding the embodiment 4as described below, the tab suspension leads 4 are designed to have asupport portion 4 a supporting the tab 5 and more than one exposedportion 4 b that is coupled thereto and is exposed to the back surface12 a of the sealing member 12, wherein the support portion 4 a is formedto be thinner than the exposed portion 4 b.

In addition, these plurality of tab suspension leads 4 are coupledtogether via the tab 5, and the exposed portion 4 b of tab suspensionleads 4 is the same in thickness as the thick portion 2 a of leads 2.

Specifically, a respective one of the plurality of tab suspension leads4 consists essentially of a support section 4 a that is coupled to thetab 5 and is substantially the same in thickness as this tab 5 and morethan one exposed portion 4 b that is coupled to this support section 4 aand is greater in thickness than the support section 4 a while causingthe plurality of tab suspension leads 4 to be integrally coupledtogether via the tab 5. Accordingly, the tab suspension leads 4 are eachprovided with a step-like level difference due to the presence of suchthick portion (exposed section 4 b) and thin portion (support section 4a) with the plurality of tab suspension leads 4 being linked togethervia the tab 5.

Whereby, the support section 4 a at the tab suspension leads 4 is buriedor embedded within the sealing member 12 whereas the exposed section 4 bis exposed at corner end portions of the back surface 12 a of thesealing member 12.

It should be noted that fabrication of a step-like difference due to thepresence of the thick portion 2 a and thin portion 2 b at leads 2 of QFNpackage 49 (patterning for formation of thick portion 2 b) andfabrication of a step-like difference due to the support section 4 a andexposed sections 4 b at tab suspension leads 4 (patterning for formationof support section 4 a) may be performed by etching techniques (e.g.half-etching treatment) as in an embodiment 11, to be described later inthe description, or alternatively by press machining such as coilingprocess as in such later-discussed embodiment 11, by way of example.

An explanation will next be given of an assembly method of the QFNpackage 49 with reference to a process flow diagram shown in FIG. 33along with sectional flow diagrams shown in FIG. 34.

Firstly, prepare a matrix lead frame 14 (see FIG. 11) which is a leadframe comprising a tab 5 capable of supporting a semiconductor chip 8,tab suspension leads 4 having a support section 4 a supporting the tab 5and more than one exposed section 4 b that is coupled to the supportsection 4 a and is greater in thickness than support section 4 a, aplurality of leads 2 as laid out around the tab 5 with a thick portion 2a and thin portion 2 b thinner than portion 2 a for formation of astep-like difference or stepped portion with respect to the thicknessdirection (at step 51).

Subsequently, after having coated or “painted” an adhesive 9, adhere thetab 5 and semiconductor chip 8 together as shown in FIG. 34A. Morespecifically, perform die bonding for fixation of the semiconductor chip8 to the tab 5 via the adhesive 9 as coated on the tab 5 (step 52).

Further, as shown in FIG. 34B, perform wire bonding as shown at step S3for connection between pads 7 of the semiconductor chip 8 and theircorresponding leads 2 by use of wires 10 that are employed asinterconnect members.

Here, use wire bonding techniques to connect the pads 7 of semiconductorchip 8 to thin portions 2 b of corresponding leads 2 via wires 10 madeof gold or else.

Thereafter, perform molding as shown at step S4 thereby forming asealing member 12 as shown in FIG. 34C.

During said bolding, the semiconductor chip 8 is resin-molded by amethod including the steps of covering both the thin portions 2 b ofleads 2 and the support section 4 a of tab suspension leads 4 with asealing resin material 11 while letting such seal resin 11 flow onto a,surface (referred to hereafter as back surface 5 b) on the opposite sideto a chip support surface 5 a of the tab 5, with the thick portions 2 aof the plurality of leads 2 and the exposed portions 4 b of tabsuspension leads 4 being disposed at the periphery on the back surface12 a.

Whereby, the semiconductor chip 8 and wires 10 along with the tab 5 andsupport section 4 a supporting the tab 5 plus the thin portions 2 b ofleads 2 are buried in the sealing member 12.

Thereafter, as shown in FIG. 34D, apply external packaging processing tothe leads 2 that are exposed on the back surface 12 a of the sealingmember 12 for the purpose of improvement in mountability when mountingthe QFN package 49 on a mount substrate 27 (see FIG. 23). This makes itpossible to insure the stand-off corresponding to the thickness of ametallized portion(s) 13. Note here that although said externalpackaging is preferably done by solder metallization techniques usingPb—Sn-based solders, other metallization methods using Pb-free solderssuch as Sn—Ag or Sn—Zn-based soldering materials may also be employablewhen the need arises.

Thereafter, cutting is done as shown at step 55.

Here, subdivide the tab suspension leads 4 into portions at the exposedportions 4 b of tab suspension leads 4 while substantiallysimultaneously separating the plurality of leads 2 from a frame section14 a of the matrix lead frame 14 (lead frame), thus completing the QFNpackage 49 as shown in FIG. 34E (at step S6).

In accordance with the QFN package 49 of the embodiment 3 and itsmanufacturing method stated supra, it is possible, by providing thestep-like difference, i.e. the thick portion 2 b and thin portion 2 a,at the leads 2 while letting the thin portion 2 b be embedded within thesealing member 12, to prevent accidental dropdown detachment of leads 2from the sealing member 12 in a direction along the height of the QFNpackage, which in turn makes it possible to prevent unwanted pull-out ordiscomposition of such leads 2 from the sealing member 12.

In addition, it is possible to set metal mold's clamp planes at the samesurface level during molding, because of the fact that the exposedsections 4 b which are exposed portions of the tab suspension leads 4and the thick portions 2 a which are exposed portions of the leads 2 areformed to have the same thickness.

More specifically, in cases where the exposed portions of the tabsuspension leads 4 (exposed portions 4 b) and exposed portions of theleads (thick portions 2 a) are different in thickness from each other,the sealing resin material 11 can flow into the thinner part sideresulting in occurrence of a need to cut both metals and resin (sealingresin 11) together at a lead cut process step thus leading to risks ofcreation of defects; on the contrary, if the exposed portions 4 b of tabsuspension leads 4 and the thick portions 2 a of leads 2 are formed tohave the same thickness then the sealing resin 11 will no longer bedisposed at cutting locations, which in turn makes it possible tofacilitate smooth effectuation of the intended lead cutting processes.

Thus, it is possible to suppress creation of defects during lead cuttingprocesses.

Embodiment 4

FIG. 35 is a diagram showing a perspective view of an exteriorappearance of an exemplary structure of a semiconductor device inaccordance with an embodiment 4 of the invention; FIG. 36 shows a bottomview of the structure of the semiconductor device shown in FIG. 35; FIG.37 is a cross-sectional view of the semiconductor device shown in FIG.35 taken along line M-M; FIG. 38 is a sectional view of thesemiconductor device shown in FIG. 35 taken along line N-N; and FIG. 39is a partial sectional view of one exemplary state at a wire-bondingprocess step during assembly of the semiconductor device shown in FIG.35.

The semiconductor device of the embodiment 4 is a QFN package 50 that isessentially similar to the semiconductor device as has been explained inconjunction with the embodiment 3 above.

One significant feature of the QFN package 50 shown in FIGS. 35-38 isthat a plurality of tab suspension leads 4 has a support section 4 a foruse in supporting a tab 5 and also exposed portions 4 b that are coupledthereto and exposed to the back surface 12 a of a sealing member 12,wherein the support section 4 a is formed so that it is thinner than theexposed portions 4 b while causing said tab suspension leads 4 becoupled together via the tab 5.

More specifically, as shown in FIG. 37, the tab suspension leads 4 aredesigned so that these are integrally coupled together via the tab 5while causing the support section 4 a of relatively reduced thicknessand exposed portions 4 b of relatively increased thickness to be formedin the tab suspension leads 4, wherein the exposed portions 4 b whichare thick portions in the tab suspension leads 4 are disposed at fourcorner edge portions of the back surface 12 a of the sealing member 12as shown in FIG. 36,

With such an arrangement, the support section 4 a in the tab suspensionleads 4 is covered by a sealing resin material 11 while simultaneouslypermitting the exposed portions 4 b to be disposed at the corner edgeportions of the back surface 12 a of the sealing member 12.

In addition, as shown in FIG. 37, a chip support surface 5 a of the tab5 and chip mount side surfaces 4 c of the tab suspension leads 4 areformed on the same flat plane.

To be brief, the QFN package 50 of this embodiment 4 is for minimizationof exposure of the tab suspension leads 4 to the pack surface 12 a ofsealing member 12 to thereby prevent undesired electrical shortingbetween such-tab suspension leads 4 and neighboring leads 2 associatedtherewith during mounting of a parts mount substrate; to this end, thisembodiment is arranged so that the remaining portions (support portion 4a) of the tab suspension leads 4 other than the exposed portions 4 b asexposed to the corner edges of the sealing member 12 are buried orembedded within the sealing member 12.

Accordingly, the exposed portions 4 b that are thick portions in the tabsuspension leads 4 come to have those portions at which any sealingresin 11 is not disposed and which consists of only metals—here, the tabsuspension leads 4 will later be subject to lead cutting processes.

Additionally, the support section 4 a of tab suspension leads 4 isformed to be less in thickness than the exposed portions 4 b by usingeither etching techniques (half-etching treatment) or press machiningsuch as coiling methods, rather than by using tab-up processing throughbend machining, to thereby ensure that the support surface 5 a of thetab 5 and the chip mount side surfaces 4 c of the tab suspension leads 4are formed on the same flat plane; thus, the tab 5 and the supportsection 4 a of tab suspension leads 4 are formed to have the samethickness as shown in FIG. 37.

One example is that when the exposed portions 4 b of tab suspensionleads 4 measure approximately 0.2 mm in thickness, the tab 5 and thesupport section 4 a which is the same in thickness as tab 5 have athickness ranging from about 0.08 to 0:1 mm (cutaway amount is 0.1 to0.12 mm).

Additionally, as shown in FIG. 38, the tab 5 supporting thereon asemiconductor chip 8 is formed so that it is smaller in size than thesemiconductor chip 8. In other words the QFN package 50 is the one ofsmall size tab structure.

Accordingly, with the QFN package 50, the tab 5 and the semiconductorchip 8 are rigidly secured (die-bonded) together by adhesive 9 such assilver paste at specified portions (positions) lying inside of bondingpads 7 of the semiconductor chip 8.

It thus becomes possible during wire bonding to reliably support theperiphery of a back surface 8 b (the opposite surface to a principalsurface 8 a on which semiconductor integrated circuitry is fabricated)of the semiconductor chip 8 by a bonding stage 20 as shown in FIG. 39.

Additionally a manufacturing method of the QFN package 50 of theembodiment 4 is substantially the same as that of the QFN package 49 ofthe embodiment 3, except that when letting a semiconductor chip 8 beadhered to its associated tab 5 at the die bonding process step, thesemiconductor chip 8 is brought into contact with the tab 5 at locations(regions) inside of its pads 7.

Furthermore, when performing braking (cutting) of tab suspension leads 4at the lead cutting step, only metal portions that do not contain anysealing resin 11 are to be broken at the exposed portions 4 b of suchtab suspension leads 4.

In accordance with the QFN package 50 of the embodiment 4, letting thesupport section 4 a of the tab 5 at the tab suspension leads 4 be formedthinner than the exposed portions 4 b makes it possible to successfullypermit the support section 4 a to be covered with the sealing resin 11for embedment in the sealing member 12; thus, it is possible to achievethe intended device structure with the exposed portions 4 b beingexposed only at the corner edges on the back surface 12 a of the sealingmember 12.

Whereby, it becomes possible to form an increased clearance between theexposed portions 4 b of the tab suspension leads 4 and their neighboringleads 2 on the back surface 12 a of the sealing member 12 while at thesame time preventing electrical shorting otherwise occurring whenmounting the QFN package 50 (semiconductor device) on the parts mountsubstrate 27 (see FIG. 23) because of the fact that the tab 5 is buriedwithin the sealing member 12.

Another advantage is that since the sealing resin 11 is no longerdisposed at the exposed portions 4 b due to the fact that the exposedportions 4 b are thicker than the support section 4 a at the tabsuspension leads 4, it becomes possible to ensure that only those metalsof exposed portions 4 b which contain none of the sealing resin 11 arecut away during cutting of the tab suspension leads 4, therebypreventing creation of any possible nick or gouge defects, which in turnmakes it possible to improve the cutting performance at tab suspensionlead cutting process steps.

Still another advantage lies in an ability to improve the surfaceflatness of the tab 5 per se due to the fact that the jointing of theplurality of tab suspension leads 4 via the tab 5 permits the tab 5 tobe integrally coupled with the tab suspension leads 4 while allowingthem to be formed of a well planarized plane coupled with the chip mountside surface thereof.

As a result, it is possible to greatly facilitate the mounting of thesemiconductor chip 8 onto the tab 5 during bonding processes whilesimultaneously improving the resultant chip adhesiveness.

A further advantage is that letting the tab 5 and semiconductor chip 8be contacted together at inside locations than the pads 7 ofsemiconductor chip 8 makes it possible to support by the bonding stage20 those portions in close proximity to the ends of the back surface Bbof semiconductor chip 8.

It is thus possible to apply appropriate ultrasonic waves and/or heat tothe bonding wires 10 during wire bonding processes, thereby improvingthe reliability and adhesiveness of such wire bonding.

Embodiment 5

FIG. 40 is a diagram showing a partial plan view of one example of theresultant structure when completion of molding in a semiconductor devicein accordance with an embodiment 5 of the instant invention, whichstructure is partly broken to visualize its internal configuration forillustration purposes only; FIG. 41 depicts a cross-sectional view ofthe semiconductor device shown in FIG. 40 as taken along line P-P; FIG.42 is a partial plan view of an exemplary lead frame structure for useduring assembly of the semiconductor device shown in FIG. 40; FIG. 43 isan enlarged partial sectional view of a structure of part “T” of FIG.41; FIG. 44 is an enlarged partial sectional view for showing anexemplary lead cutting method at the part T of FIG. 41; FIG. 45 is adiagram showing a lead structure of part “Q” of FIG. 40, wherein FIG.45A is a bottom view, FIG. 45B is a plan view, FIG. 45C is a sectionalview of a groove section, FIG. 45D is a sectional view along line U-U ofFIG. 45B, FIG. 45E is a sectional view along line V-V of FIG. 45B; and,FIG. 46 is a plan view of one possible modified example of the leadstructure of part Q of FIG. 40.

Regarding the embodiment 5, an explanation will be given of the shape ofleads 2 at the QFN package 50 or the like as has been explained inconjunction with the embodiment 4, along with effects and advantagesthereof.

Note that FIG. 40 depicts an inside structure of a sealing member 12 atthe termination of a molding process while presenting it in a manner asseen transparently through the sealing member 12 and semiconductor chip8 for illustration purposes only.

In addition, a tab 5 shown in FIG. 40 is of the cross-type small tabstructure (wherein the tab 5 is smaller in size than the semiconductorchip 8).

In the semiconductor device of the embodiment 5, a respective one of theplurality of leads 2 has a to-be-connected portion 2 c as exposed to theperiphery of a back surface 12 a of the sealing member 12 and athickness reduced or “thin” portion 2 b as formed at an end on the tab 5side to be thinner than to-be-connected portion 2 c, wherein each lead 2is provided with an inner groove portion (groove) 2 e and outer grooveportion (groove) 2 f in a specified surface of the to-be-connectedportion 2 c (this surface will be referred to as a wire bonding surface2 d hereinafter) on the opposite side to the exposed side as disposedwithin the sealing member 12.

Note here that the pads 7 of semiconductor chip 8 are connected by wires10 to wire bonding surfaces 2 d of to-be-connected portions 2 c of thoseleads 2 corresponding thereto while causing the thin portions 2 b ofsuch leads 2 to be covered by a sealing resin material 11 with the wires10 being bonded to the to-be-connected portions 2 c between the outergrooves 2 f and inner grooves 2 e.

Here, the thin portions 2 b of the leads 2 of the embodiment 5 areformed into a knife-edge or “sword tip”-like shape to permit its tabside end to slightly project toward the tab 5, which shape may befabricated through etching treatment (half-etching patterning) and/orpress machining such as coiling. An exemplary amount of such projectionmay range from about 50 to 150 μm. Use of such thin portions 2 b makesit possible to prevent dropdown detachment of leads 2 in a directionalong the height of QFN package.

To be brief, it is possible to achieve prevention of pull-out of theleads 2 toward the QFN height direction.

In addition, the inner grooves 2 e as provided in the wire bond surfaces2 d of the leads 2 are for use as markings indicative of bonding pointsduring wire bonding. Accordingly, by forming such inner grooves 2 e inthe wire bonding surfaces 2 d of leads 2 in specified regions lyingoutside of the thin portions 2 b, it becomes possible to prevent thewires 10 from being bonded at such thin portions 2 b.

It should be noted that as the inner grooves 2 e are the grooves actingas the bonding point marks, the size thereof is smaller than that ofouter grooves 2 f as shown in FIG. 45.

On the other hand, the outer grooves 2 f are the locations for receivalof cutting stress forces during cutting of the leads 2; during leadcutting as shown in FIG. 44, let any possible cutting stress forces beconcentrated to these outer grooves 2 f to ensure that no such forcesare hardly applied to bonding portions of the wires 10.

Furthermore, the outer grooves 2 f are the ones for use in blocking aflow of hot-melt metals for metallization on the wire bonding surfaces 2d of the leads 2 during formation of a metallized layer 21 such as at awire bonding silver metallization step as shown in FIG. 43.

In short, it is possible to permit the groove shape resulting from thepresence of outer grooves 2 f to be greater in absolute distance thanflat surfaces; thus, it becomes possible to increase the leak passlength when forming said metallized part, thereby enabling prevention ofany unwanted flow of melted metals used therefor.

Furthermore, as it is possible to permit the groove shape due to theouter grooves 2 f to be greater in absolute distance than flat surfaces,it is also possible to prevent immersion or “invasion” of watercomponent into the sealing member 12.

Additionally, as shown in FIG. 45B, the outer grooves 2 f are formed sothat these are greater in size than the inner grooves 2 e. This makes itpossible to reliably perform both prevention of unwanted concentrationof stress forces during lead cutting and also undesired metal flowageduring metallization processes.

Note however that the dimensions and shape of the outer grooves 2 f andinner grooves 2 e should not be limited to those discussed above and mayalternatively be modified so that the both of them have an ellipticalshape of the same size as shown in FIG. 46, by way of example.

In addition, as shown in FIGS. 45D and 45E the leads 2 are such thateach is provided on its side surfaces with knife edge portions 2 g whichare projected by little toward the width direction thereof.

Use of such knife edge portions 2 g makes it possible to prevent theleads 2 from attempting to drop down in a direction along the height ofQFN package. In other words, it is possible to prevent pull-outdetachment of such leads 2 toward the QFN height direction.

Further, provision of the inner grooves 2 e and outer grooves 2 f in thewire bonding surfaces 2 d of leads 2 permits the sealing resin material11 to enter and fill the both groove portions; thus, it is possible toprevent unwanted dropdown detachment of the leads 2 in the elongatedirection thereof (QFN horizontal direction at right angles to the QFNheight direction). In short, it is possible to prevent pullout of theleads 2 toward the extending direction thereof.

It should be noted that in accordance with a method of manufacturing thesemiconductor device of the embodiment 5, the pads 7 of semiconductorchip 8 are connected by wires 10 to specified portions lying between theinner grooves 2 e and outer grooves 2 f at the to-be-connected portions2 c of leads 2 as shown in FIG. 41 when connecting by wire bondingtechniques the pads 7 of semiconductor chip 8 to the to-be-connectedportion 2 c of corresponding leads 2 during a wire bonding process.

Also note that regarding the inner grooves 2 e and outer grooves 2 f,both of them will not necessarily provided at a time and either one ofthem may be employed on a case-by-case basis.

One example is that only the outer groove 2 f which is a single groovemay be provided in the wire bonding surface 2 d of a lead 2; if this isthe case, a wire 10 will be bonded for electrical connection to itsassociated to-be-connected portion 2 c at an inside location relative tothe outer groove 2 f.

Whereby, it is possible to prevent concentration of stress forces duringlead cutting while simultaneously eliminating any irregular metalflowage during metallization processes in the same way as that statedsupra.

Note that only the inner groove 2 e which is a single groove may beprovided in the wire bonding surface 2 d of a lead 2; in such case, awire 10 will be bonded to a to-be-connected portion 2 c at part lyingoutside of the inner groove 2 e.

This in turn makes it possible to perform the intended wire bonding atan appropriate location with the inner groove 2 e being used as abonding point marking during wire bonding.

Embodiment 6

FIG. 47 is a diagram showing an enlarged partial plan view of astructure of part “R” of FIG. 40, which has been explained inconjunction with the embodiment 5 above.

Regarding the embodiment 6 also, an explanation will be given of theshape of leads 2 at the QFN package 50 or the like as has been explainedin conjunction with the embodiment 4 along with effects and advantagesthereof, in a similar way to the embodiment 5.

The embodiment 6 is directed to a case where certain leads 2 of theplurality of leads 2 which are disposed neighboring a tab suspensionlead 4 and placed on the opposite sides thereof are taken up, wherein atapered section (cutaway portion) 2 h is provided at a selected distalend of each lead 2 opposing the tab suspension lead 4 for formation of agap 2 i lying between the lead 2 and tab suspension lead 4 and extendingalong this lead 4.

This taper section 2 h is a cutaway portion for formation of the gap 2 ias required for effectuation of necessary processes when forming a leadpattern by etching treatment or press machining techniques—for example,a gap of about 80% of a lead plate thickness will be required forpatterning purposes.

In particular, when the layout density of those leads 2 as disposedbetween tab suspension leads increases as a result of an increase inrequisite number of pins used, the tab suspension lead side distal endof a lead 2 neighboring a tab suspension lead 4 comes closer to the tabsuspension lead 4 so that it will become impossible or at least greatlydifficult to perform the intended patterning of such tab suspension lead4 or alternatively its neighboring lead 2.

Accordingly, by providing the taper section (cutaway portion) 2 h forformation of the gap 2 i at the tab suspension lead side distal endportion of the lead 2 in close proximity in position to the tabsuspension lead 4, it becomes possible to fabricate any intended leadpattern of those leads 2 as disposed adjacent to tab suspension leads 4while at the same time making it possible to cope with an increase inrequisite number of pins used.

Embodiment 7

FIG. 48 is a diagram showing a structure of part “S” of FIG. 40 as hasbeen explained in conjunction with the embodiment 5, wherein FIG. 48A isan enlarged partial plan view whereas FIG. 48B is a sectional view ofFIG. 48A as taken along line X-X; and FIG. 49 is a diagram showing astructure of part “W” of FIG. 48A, wherein FIG. 49A is an enlargedpartial plan view and FIG. 49B is a groove sectional view of FIG. 49A.

In regard to the embodiment 7, an explanation will be given of the shapeof leads 2 at the QFN package 50 or the like as has been explained inconjunction with the embodiment 4, along with effects and advantagesthereof.

The embodiment 7 is directed to a case where the plurality of (four) tabsuspension leads 4 for use in supporting a tab 5 are designed so thateach of the tab suspension leads 4 comprises an exposed portion 4 b asexposed to an end portion of a back surface 12 a of a sealing member 12and a groove portion 4 d which is a thickness-reduced or “thin” portionbridging between the inside and outside of a molding line 12 b (outerperiphery) of the sealing member 12.

Note here that a molding metal frame structure's gate 26 (see FIG. 19)is formed at a nearby location corresponding to the mold line 12 b ofthe tab suspension leads 4; accordingly, a sealing resin material 11 isformed to have an increased thickness at or near such location resultingin that the tab suspension leads 4 are cut in a way that resemblesbreaking (pull-put destruction) at lead cutting process steps.

Accordingly this groove 4 d is a notch (cutaway) for permittingconcentration of stress forces to thereby ensure that the breaking(cutting) of the tab suspension leads 4 is readily done during leadcutting processes, which notch is formed at a preselected locationcorresponding to the mold line 12 b of the sealing member 12 of the tabsuspension leads 4 (region linking between the inside and outside of themold line 12 b) for giving a chance during breaking of the tabsuspension leads.

Further, as shown in FIGS. 48A and 48B, the groove 4 d is formed in theexposure side surface of a tab suspension lead 4 lying on the oppositeside to a chip mount side surface 4 c thereof.

In other words the groove 4 d is formed in the surface of tab suspensionlead 4 corresponding to the back surface 12 a side (back side) of thesealing member 12.

Whereby, it is possible to prevent the sealing resin 11 from attemptingto enter the interior of the groove 4 d, which in turn makes it possibleto preclude creation of nick defects otherwise occurring due to floatingof resin (sealing resin 11) junk components and also punching abrasiondue to resin cutting.

It is thus possible to achieve longer lifetime of a lead cutting punch54 (see FIG. 44).

In addition, as shown in FIGS. 49A and 49B, the groove 4 d is formedinto an elliptical shape that is lengthened in the elongate direction ofa tab suspension lead 4, and further is surrounded by a sidewall 4 e.

This is as a result of taking into consideration any possible deviationof the formation position of a sealing member 12 during molding, and isalso for making sure that the groove 4 d exactly overlies the mold line12 b by fabrication of the groove 4 d into an elliptical shape aslengthened in the elongate direction of tab suspension lead 4 (byletting CD>EF as shown in FIG. 49A, obtain a long narrow circular shapein the lead extension direction).

Further, by forming the sidewall 4 e (JK) shown in FIG. 49A on the bothsides of such elliptically shaped groove 4 d in the lead widthdirection, it is possible to prevent generation of chance inhibition atthe time of cutting leads due to entrance or “invasion” of resin wastageinto the groove 4 d.

Furthermore, as it is possible by the presence of the sidewall 4 e toprevent invasion of resin wastage into the groove 4 d, it becomespossible to prevent unwanted creation of nick defects due to resinwastage floating and also punching abrasion due to resin cutting, in thesame way as has been stated previously.

It should be noted that in accordance with a method of manufacturing thesemiconductor device of the embodiment 7, the sealing member 12 isfabricated through resin molding processes while letting the groove 4 dof tab suspension lead 4 correspond to the mold line 12 b (outerperiphery) of the sealing member 12 at a molding process step.

More specifically the sealing member 12 is formed to ensure that theellipse-shaped groove 4 d at the tab suspension lead 4 is disposedbridging between the inside and outside of the mold line 12 b.

With such an arrangement, it is possible by the presence of such groove4 d to give a chance to lead breaking destruction during lead cutting(breaking).

Embodiment 8

FIG. 50 is a diagram showing an exemplary structure of a semiconductordevice in accordance with an embodiment 8 of this invention, whereinFIG. 50A is a plan view, FIG. 50B is a side view, and FIG. 50C is abottom view; and FIG. 51 is an enlarged partial bottom view of astructure of part “Y” of FIG. 50C.

In the embodiment 8, an explanation will be given of a relation betweenthe length of a to-be-connected portion 2 c of a lead 2 in a QFN package51 shown in FIGS. 50A-50C that is similar to the QFN package 50 as setforth previously in conjunction with the embodiment 4, which portion 2 cis exposed to the periphery of the back surface 12 a of a sealing member12, and the length of an exposed portion 4 b of a tab suspension lead 4as exposed to a corner edge portion of the back surface 12 a of thesealing member 12, along with effects and advantages thereof.

The embodiment 8 is the case where the length of the exposed portion 4 bof tab suspension lead 4 in its elongate direction is formed to beshorter than the length of the to-be-connected portion 2 c of lead 2 inthe elongate direction thereof.

More specifically, let the length (LX) of the exposed portion 4 b of tabsuspension lead 4 be maximally shortened as shown in FIG. 51. This isfor prevention of an increase in possibility of creation of electricalshorting when mounting a parts-mount substrate, which can occur due toapproaching in distance of the exposed portion 4 b of tab suspensionlead 4 toward its associative leads 2 as adjacently disposed on theopposite side thereof in cases where the requisite number of leads isincreased in those packages of the same size.

Accordingly, let the length (LX) of the exposed portion 4 b of tabsuspension lead 4 be formed so that it is shorter than the length (LP)of the to-be-connected portion 2 c of lead 2 (LX<LP). Furthermore, itwill be preferable that a relation of a distance (LY) between theto-be-connected portion 2 c of a lead 2 neighboring the tab suspensionlead 4 and the exposed portion 4 b of such tab suspension lead 4 versusa distance (12) between neighboring leads be designed to satisfy(LY)(12).

With such an arrangement, it is possible to prevent electrical shorting(bridging) otherwise occurring due to the presence of any residualsolder materials when mounting a parts-mount substrate of the QFNpackage 51.

Embodiment 9

FIG. 52 is a diagram showing a partial plan view of an exemplarystructure of a semiconductor device in accordance with an embodiment 9of the invention as obtained at termination of molding, the structurehaving an internal configuration as seen through a seal section thereof;FIG. 53 is a cross-sectional view of the semiconductor device shown inFIG. 52 as taken along line Z-Z; FIG. 54 is an enlarged partialsectional view of a structure of the device at part “AB” of FIG. 53; andFIG. 55 is an enlarged partial sectional view diagram showing oneexample of a method of cutting leads at the part “AB” of FIG. 53.

In the embodiment 9, an explanation will be given of the shape of leads2 in a semiconductor device that comprises a plurality of leads 2 havingextension portions 2 j that extend toward the center of a tab 5 or itsnearby part and are disposed in close proximity thereto, along witheffects and, advantages thereof.

Note that FIG. 52 is the one that depicts an inside structure of asealing member 12 obtained at the termination of molding as seentransparently through the sealing member 12 and a semiconductor chip 8for illustration purposes.

The semiconductor device of the embodiment 9 is arranged so that arespective one of the plurality of leads 2 as disposed around a tab 5has an extended portion 2 j extending toward the center of such tab 5 orits nearby part and is laid out in close proximity thereto and ato-be-connected portion 2 c as exposed to the periphery of a backsurface 12 a of the sealing member 12, wherein the extension 2 j of eachlead 2 is formed to be thinner than the to-be-connected portion 2 c andis covered by a sealing resin material 11, and wherein a lead grooveportion (groove) 2 k is formed in a wire bonding surface 2 d that is asurface of the to-be-connected portion 2 c on the opposite side to anexposure side as disposed within the sealing member 12.

Additionally the semiconductor device of the embodiment 9 is the onewhich is structurally designed so that the extension 2 j is provided ata tab side end of each lead 2 for extending this lead to therebyeliminate increase in distance between the leads 2 and semiconductorchip 8 when enlargement of a package and shrinkage of semiconductor chip8 due to an increase in pin number would result in an increase indistance between lead 2 and semiconductor chip 8.

Accordingly each lead 2 is provided at its tab side end with anextension 2 j extending toward the center of the tab 5 or its nearbylocation (toward its corresponding pad 7), thus facilitating bonding ofa wire 10 thereto.

More specifically each lead 2 is formed into a shape that is radiallyextended from nearby periphery of the tab 5 toward the outside as shownin FIG. 52.

Whereby, it will no longer happen that wires increase in length evenwhen the package size is enlarged and/or when an attempt is made tominiaturize or “shrink” the semiconductor chip 8, which in turn makes itpossible to suppress an increase in production cost.

It should be noted that since the length (LP) of the to-be-connectedportion 2 c as exposed to the back surface 12 a of the sealing member 12is defined by the EIAJ standards as shown in FIG. 54, the extension 2 jmust be buried or embedded within the sealing member 12 in the eventthat the lead 2 is provided with such extension 2 j; in view of this,the semiconductor device of the embodiment 9 is specifically arranged sothat the extension 2 j is formed to be thinner than the to-be-connectedportion 2 c and is then embedded within the sealing member 12 withouthaving to make higher the position of the extension 2 j (withoutperforming any lead rise-up processing).

More specifically, as shown in FIGS. 53-54, the extension 2 j at eachlead 2 is formed so that it is thinner than the to-be-connected portion2 c as exposed to the back surface 12 a of the sealing member 12 and issimultaneously covered by the sealing resin 11 together with the tab 5.

Additionally the thinner formation of the extension 2 j than theto-be-connected portion 2 c makes it possible to prevent dropdowndetachment of its associative lead 2 in the thickness direction of thesealing member 12.

Further, since the extension 2 j has an increased distance in itselongate direction in comparison with the knife edge-shaped thin portion2 b shown in FIG. 41, it is also possible to dispose the bonding stage20 (see FIG. 39) at a specified location beneath the extension 2 jduring wire bonding, which in turn makes it possible to apply optimalultrasonic waves or heat to both the wires 10 and the leads 2 duringwire bonding.

Note that the extension 2 j may be formed thinner by etching treatment(half-etching patterning) or alternatively press machining techniquessuch as coiling.

Also note that as shown in FIG. 54, a lead groove portion (groove) 2 kis formed at a selected location of the to-be-connected portion 2 c ofeach lead 2 near the outside of the wire bonding surface 2 d (surface onthe opposite side to the exposure side) that is laid out within thesealing member 12.

This lead groove 2 k is the same in function to the outer groove portion2 f (see FIG. 43) as has been explained in conjunction with theembodiment 5; thus, it is possible to concentrate cutting stress forcesto this lead groove 2 k during cutting processes using a punch 54 shownin FIG. 55, thereby preventing such stresses from being applied tobonding portions of wires 10.

Further, the presence of the lead groove 2 k makes it possible to blocka flow of hot-melt metals when forming a metal-plated layer 21 such as asilver-metallized one used for wire bonding purposes as shown in FIG.54.

Furthermore, as it is possible to permit a groove shape due to presenceof the lead groove 2 k to offer a longer absolute distance than flatsurfaces; thus, it becomes possible to prevent unwanted invasion ofwater component into the sealing member 12 also.

In addition, as the sealing resin 11 attempts to enter the lead groove 2k due to molding, it is possible to prevent dropdown detachment of leads2 with respect to the elongate direction of such leads 2. Thus, itbecomes possible to prevent pull-out of leads 2 toward the elongatedirection thereof.

Embodiment 10

FIGS. 56A-56D, FIGS. 57A-57D, and FIGS. 58A-58D are partial sectionaldiagrams showing a patterning method using etch techniques as oneexample of a lead frame machining method used for assembly of thesemiconductor device in accordance with the invention.

The embodiment 10 is for explanation of one exemplary patterning methodof leads 2 and tab 5 of any one of the semiconductor devices as statedsupra in conjunction with the embodiments 1 to 9, etching treatment(half-etching patterning) will be explained.

It must be noted that etching liquid or etchant 52 as used during etchpatterning of the embodiment 10 is liquid solution of iron (II) oxide orelse, although not exclusively limited thereto.

FIGS. 56A-56D show a method (procedure) of fabricating the intendedsectional shape or “profile” of leads 2 such as shown in FIG. 45E forexample; FIGS. 57A-57D show a method (procedure) of fabricating theprofile of leads 2 such as shown in FIG. 45D by way of example.

More specifically, in FIGS. 56 and 57, the etching amount on the top andbottom surfaces of leads 2 is appropriately adjusted by changing orvarying the opening width (aperture area) of certain parts (portions “A”and “B”) whereat a photo resist film 53 is not formed, thus enablingobtainment of respective sectional shapes.

In the patterning processes shown in FIG. 56, A is nearly equal to (=)Band G=H; thus, C=D, E=F.

Alternatively in the processes shown in FIG. 57, A<B and I>J; thus C<D,E>F.

In addition, FIGS. 58A-58D show a method (procedure) of back-surfaceprocessing of the tab 5 shown in FIG. 53 and also performing thinningprocessing of extensions 2 j of leads 2, for example.

More specifically, as shown in FIG. 58A, fabricate a photo resist film53 at fine pitch (B) only on the processing surface side of the tab 5and the like; then, as shown in FIG. 58(b), coat or “paint” etchingliquid 52 only on said processing side, thereby realizing the intendedback-surface processing of-the tab 5 and the thinning processing of theextensions 2 j of leads.

Embodiment 11

FIGS. 59A-59C, FIGS. 60A-60C, and FIGS. 61A-61C are partial sectionaldiagrams showing press methodology as one example of a lead framemachining method used for assembly of the semiconductor device of theinvention.

The embodiment 11 is for explanation of one example of the processingmethod of the leads 2 and tab 5 of the semiconductor devices as has beenexplained in conjunction with the embodiments 1 to 9 stated supra—here,press machining such as coiling will be explained below.

FIGS. 59A-59C show a method (procedure) of performing by press machiningtechniques the back-surface processing of the tab 5 shown in FIG. 53 forexample; FIGS. 60A-60C show a method (procedure) of performing thinningof the extensions 2 j of leads 2 shown in FIG. 53 by press machiningtechniques, by way of example.

In other words, the both of them are for thinning either the tab 5supported by a receiving base or pedestal 55 or the leads 2 or elsethrough coiling by use of a punch 54.

Note that in this processing method, said coiling may be carried out atthe beginning of raw material processing; or alternatively, said coilingmay be applied to only necessary portions after completion offabrication of a lead frame pattern.

In addition, FIGS. 61A-61C show a method (procedure) of forming the leadprofile as shown for example in FIG. 45D by use of press machiningtechniques.

More specifically, as shown in FIG. 61A, after having thinned throughcoiling using the punch 54 the leads 2 as supported by the pedestal 55,as shown in FIGS. 61B and 61C, unnecessary portions are cut away forremoval, thereby enabling obtainment of any desired sectional shapes ofthe leads 2.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, the invention should not belimited only to such embodiments, and it will be understood by thoseskilled in the art that the foregoing and other changes in form anddetails may be made therein without departing from the spirit and scopeof the invention.

For example, although said embodiments 1 to 11 stated supra are arrangedso that the tab 5 is of a circular or cross-like shape, the shape ofsuch tab 5 should not be limited thereto and may be replaced with anyone of those for use in semiconductor devices in accordance withmodified examples as shown in FIGS. 62 and 64.

The tab 5 shown in FIGS. 62 and 63 is designed to have a small tabstructure by quartering; in this case, it is possible to improve theshrinkability of such tab 5 in the horizontal direction (directionhorizontal relative to tab suspension leads 4) to thereby improve thetemperature cycling characteristics of semiconductor devices, which inturn makes it possible to reduce chip cracking and/or package crackingaccidents.

In addition, the tab 5 shown in FIG. 64 is designed to have aframe-shaped small tab structure; in this case, as it is possible toincrease the bonding area of a sealing resin material 11 and the backsurface 8 b of a semiconductor chip 8, it becomes possible to suppresspeel-off of the semiconductor chip 8 and others.

It should be noted that although in said embodiments 1 to 11 the leadframe used therein is the matrix lead frame 14, said lead frame mayalternatively be modified to employ a multi-string configuration withthe unit lead frames 15 being laid out into a single linear array.

It should also be noted that although in said embodiments 1-11 thesemiconductor device used is a small size QFN package, saidsemiconductor device may be modified to those semiconductor devices ofthe types other than the QFN as far as they are of the peripheral typeas assembled using the lead frame.

INDUSTRIAL APPLICABILITY

Effects and advantages obtainable by representative ones of theinventive teachings as disclosed herein will be explained in briefbelow.

(1) As it is possible to form a stepped portion or portions throughhalf-etching patterning processes rather than formation of such steppedportions through bend/fold machining (up-set processing) to therebypermit existence of a sealing resin material at there, it becomespossible to successfully seal the tab and the tab suspension leads withthe sealing resin while at the same time achieving the intendedthickness-reduced or thinned structure, which in turn makes it possibleto avoid the problem as to degradation of reliability due to decrease inadhesion strength as resulted from reduction of the contact area betweenthe sealing resin and the tab.

(2) Since the lower surfaces of leads are forced to be exposed from thelower surface of a semiconductor device and are then used as externalconnection terminals, it is possible to prevent unwanted deformation ordistortion of such leads in carriage and/or mounting events, therebyimproving the reliability.

(3) As the leads used are designed to be projected very little from theside surfaces of a sealing section, it becomes possible for thesemiconductor device to shrink in planar size.

(4) As the leads are formed to have their sealed or hermetic uppersurfaces wider than exposed lower surfaces thereof, it is possible toattain sufficiently increased adhesiveness irrespective of the fact thatthe resulting bonding surfaces with the sealing resin consist of upperand side surfaces only, thereby enabling retainment of the reliabilityrequired.

(5) As the stepped portion-of a matrix lead frame is fabricated throughsimultaneous execution of patterning and half-etching treatmentprocesses unlike the prior art approaches which have been designed tofabricate it through post-processing after completion of either punchingor patterning using etch techniques of a metal plate, it is possible toreduce production costs of such matrix lead frame.

(6) As the matrix lead frame does no longer require effectuation of anybend/fold processes with respect to the matrix lead frame aftercompletion of patterning as has been employed in the prior art, itbecomes possible to prevent occurrence of problems such as tabdislocation defects or the like due to such folding processes.

(7) As, unlike the prior art, it is no longer required to applybend/folding processes to the semiconductor device's external terminals,the requisite number of process steps may be reduced thereby makingeasier the process management to thereby improve the productivity.

(8) In all processes concerned, the currently established semiconductormanufacturing apparatus or equipment is employable for fabrication ofthe semiconductor device of the invention without requiring anysubstantive alterations thereto, which advantageously serves toeliminate or at least minimize risks of capital investment of newfacility.

(9) As the stepped portion is formed by applying half-etching treatmentto the lower surfaces of inner ends of leads and then sealing them witha sealing resin material, it is possible to optimally design the shapeand lead pitch values in a way conformity with the semiconductor chipsize and the number of pads thereof.

(10) As the tab support section at tab suspension leads is formed to bethinner than the exposed portion, it is possible to attain the intendedstructure with the exposed portion being exposed only to corner edgeportions of the back surface of a sealing section. Whereby, it ispossible to increase or maximize the clearance as defined on the backsurface of the seal section between the exposed portions of the tabsuspension leads and its neighboring leads; in addition, arranging thetab to be embedded within the seal section makes it possible to preventelectrical shorting otherwise occurring when mounting a semiconductordevice onto a parts-mount substrate.

(11) As the sealing resin is by no means disposed at the exposed portiondue to the fact that the exposed portion is thicker than the supportsection in the tab suspension leads, only target metal components of theexposed portion containing no sealing resin materials will be cut duringtab suspension lead cutting processes; as a result, it is possible toimprove the cutting performance and reliability at such tab suspensionlead cutting steps.

(12) As the tab suspension leads are coupled together via a tabresulting in integral linkage between the tab and the tab suspensionleads while permitting formation by a flat plane coupled to its chipmount side surface, the surface flatness of the tab per se may beimproved. As a result, it is possible to make easier the procedure ofmounting a semiconductor chip onto the tab during bonding whilesimultaneously improving the chip adhesiveness.

(13) As the tab and its associative semiconductor chip are bondedtogether at a selected location lying inside of an array of surfaceelectrodes of the semiconductor chip, it is possible to stably supportby a bonding stage those portions at or near the end portions on theback surface of the semiconductor chip. Thus, it is possible to applyadequate ultrasonic waves and/or heat to bonding wires during wirebonding, thereby making it possible to improve the reliability andadhesiveness of wire bonding processes.

What is claimed is:
 1. A semiconductor device, comprising: a die pad; asemiconductor chip disposed on the die pad, the semiconductor chipincluding a main surface on which a plurality of pads are formed; aplurality of suspension leads connected with the die pad; a plurality ofleads arranged around the die pad in plan view and also arranged betweenthe plurality of suspension leads in plan view; a plurality of wireselectrically connecting the plurality of pads of the semiconductor chipwith the plurality of leads, respectively; and a seal portion sealingthe semiconductor chip and the plurality of wires, wherein in the sealportion, the plurality of suspension leads are extended toward cornerportions of the seal portion from a central portion of the seal portion,respectively, wherein in the seal portion, the plurality of leads areonly extended in first directions perpendicular to sides of the sealportion, respectively, wherein the seal portion includes a front surfacelocated at a same side as the main surface of the semiconductor chip,and a rear surface opposite to the front surface, wherein each of theplurality of leads includes a wire connection surface located at thesame side as the main surface of the semiconductor chip, and a backsurface opposite to the wire connection surface and also exposed fromthe rear surface of the seal portion, wherein the plurality of leadsincludes a first lead adjacent to a first suspension lead of theplurality of suspension leads, and a second lead adjacent to the firstlead and also arranged farther than the first lead from the firstsuspension lead, wherein the back surface of the first lead includes afirst side located beside the first suspension lead, and a second sideopposite to the first side, wherein the back surface of the first leadfurther includes a first corner portion closest to the first suspensionlead, and wherein the first corner portion is chamfered such that alength of the first side is shorter than a length of the second side. 2.The semiconductor device according to claim 1, wherein the back surfaceof the second lead includes a third side adjacent to the second side ofthe first lead, and a fourth side opposite to the third side, andwherein a length of the third side is substantially equal to a length ofthe fourth side.
 3. The semiconductor device according to claim 2,wherein the length of the second side is substantially equal to thelength of each of the third and fourth sides.
 4. The semiconductordevice according to claim 2, wherein a length of the third side is equalto a length of the fourth side.
 5. The semiconductor device according toclaim 4, wherein the length of the second side is substantially equal tothe length of each of the third and fourth sides.
 6. The semiconductordevice according to claim 4, wherein the length of the second side isequal to the length of each of the third and fourth sides.
 7. Thesemiconductor device according to claim 1, wherein the upper surface ofthe suspension part is located at the same level as the wire connectionsurface of each of the plurality of leads.
 8. The semiconductor deviceaccording to claim 7, wherein the back surface of the second leadincludes a third side adjacent to the second side of the first lead, anda fourth side opposite to the third side, and wherein a length of thethird side is substantially equal to a length of the fourth side.
 9. Thesemiconductor device according to claim 8, wherein the length of thesecond side is substantially equal to the length of each of the thirdand fourth sides.
 10. The semiconductor device according to claim 8,wherein a length of the third side is equal to a length of the fourthside.
 11. The semiconductor device according to claim 10, wherein thelength of the second side is substantially equal to the length of eachof the third and fourth sides.
 12. The semiconductor device according toclaim 10, wherein the length of the second side is equal to the lengthof each of the third and fourth sides.
 13. A semiconductor device,comprising: a die pad; a semiconductor chip disposed on the die pad, thesemiconductor chip including a main surface on which a plurality of padsare formed; a plurality of suspension leads connected with the die pad;a plurality of leads arranged around the die pad in plan view and alsoarranged between the plurality of suspension leads in plan view; aplurality of wires electrically connecting the plurality of pads of thesemiconductor chip with the plurality of leads, respectively; and a sealportion sealing the semiconductor chip and the plurality of wires,wherein in the seal portion, the plurality of suspension leads areextended toward corner portions of the seal portion from a centralportion of the seal portion, respectively, wherein in the seal portion,the plurality of leads are only extended in first directionsperpendicular to sides of the seal portion, respectively, wherein theseal portion includes a front surface located at a same side as the mainsurface of the semiconductor chip, and a rear surface opposite to thefront surface, wherein each of the plurality of leads includes a wireconnection surface located at the same side as the main surface of thesemiconductor chip, and a back surface opposite to the wire connectionsurface and also exposed from the rear surface of the seal portion,wherein the plurality of leads includes a first lead adjacent to a firstsuspension lead of the plurality of suspension leads, and a second leadadjacent to the first lead and also arranged farther than the first leadfrom the first suspension lead, wherein the back surface of the firstlead includes a first side located beside the first suspension lead, anda second side opposite to the first side, wherein the back surface ofthe first lead further includes a first corner portion closest to thefirst suspension lead, wherein the first corner portion is chamferedsuch that a length of the first side is shorter than a length of thesecond side, wherein each of the plurality of suspension leads includesa suspension part connected with the die pad, and an end part fartherthan the suspension part from the die pad, wherein the suspension partincludes an upper surface located at the same side as the main surfaceof the semiconductor chip, and wherein the upper surface of thesuspension part is located at the substantially same level as the wireconnection surface of each of the plurality of leads.
 14. Thesemiconductor device according to claim 13, wherein the back surface ofthe second lead includes a third side adjacent to the second side of thefirst lead, and a fourth side opposite to the third side, and wherein alength of the third side is substantially equal to a length of thefourth side.
 15. The semiconductor device according to claim 14, whereinthe length of the second side is substantially equal to the length ofeach of the third and fourth sides.
 16. The semiconductor deviceaccording to claim 15, wherein the suspension part further includes aback surface opposite to the upper surface, wherein a thickness of thesuspension part is less than a thickness of each of the leads, andwherein the back surface of the suspension part is covered with the sealportion.
 17. The semiconductor device according to claim 15, wherein thesemiconductor chip includes a back surface opposite to the main surface,and wherein a part of the back surface of the semiconductor chipcontacts with the seal portion.
 18. The semiconductor device accordingto claim 15, wherein each of the corner portions of the seal portion ischamfered.
 19. The semiconductor device according to claim 14, wherein alength of the third side is equal to a length of the fourth side. 20.The semiconductor device according to claim 19, wherein the length ofthe second side is substantially equal to the length of each of thethird and fourth sides.
 21. The semiconductor device according to claim19, wherein the length of the second side is equal to the length of eachof the third and fourth sides.
 22. The semiconductor device according toclaim 13, wherein the upper surface of the suspension part is located atthe same level as the wire connection surface of each of the pluralityof leads.
 23. The semiconductor device according to claim 22, whereinthe back surface of the second lead includes a third side adjacent tothe second side of the first lead, and a fourth side opposite to thethird side, and wherein a length of the third side is substantiallyequal to a length of the fourth side.
 24. The semiconductor deviceaccording to claim 23, wherein the length of the second side issubstantially equal to the length of each of the third and fourth sides.25. The semiconductor device according to claim 23, wherein a length ofthe third side is equal to a length of the fourth side.
 26. Thesemiconductor device according to claim 25, wherein the length of thesecond side is substantially equal to the length of each of the thirdand fourth sides.
 27. The semiconductor device according to claim 25,wherein the length of the second side is equal to the length of each ofthe third and fourth sides.
 28. The semiconductor device according toclaim 27, wherein the suspension part further includes a back surfaceopposite to the upper surface, wherein a thickness of the suspensionpart is less than a thickness of each of the leads, and wherein the backsurface of the suspension part is covered with the seal portion.
 29. Thesemiconductor device according to claim 27, wherein the semiconductorchip includes a back surface opposite to the main surface, and wherein apart of the back surface of the semiconductor chip contacts with theseal portion.
 30. The semiconductor device according to claim 27,wherein each of the corner portions of the seal portion is chamfered.